There are different types of inhalers on the market. A pressurized Metered Dose Inhaler (pMDI) releases a fixed dose of substance in aerosol form. A powder inhaler generally releases a dose of powdered substance entrained in an air stream. In a powder inhaler the powder may be provided in a bulk container of the inhaler from which doses of powder are metered for dispensing. As an alternative to a bulk container, powder inhalers may comprise a single compartment or a plurality of compartments for containing one or more discrete doses of powdered substance. Such compartments may take the form of sealed blisters in a blister pack, a cavities-containing strip joined to a sealing strip or other suitable forms.
EP 1 220 698 discloses an inhaler for medicament in powder form. The medicament is arranged in the inhaler in a number of enclosures. When the airflow in the inhaler reaches a certain threshold value, a breath-activated activating means causes an elongated hollow body to pierce the enclosure so that the medicament is accessed.
U.S. Pat. No. 6,651,341 discloses a foil-cutting device for opening a foil protecting a dose of medical powder carried by a dosing cassette for an inhaler. When a user inhales through the inhaler the foil-cutter opens the foil for access to a pre-metered powder dose.
When a foil is cut or pierced there is a risk that small fragments of the foil material are detached and become inhaled by the user.
WO99/36116 discloses a dry powder inhaler which, in one embodiment, has a foil flap covering a medicament cavity. The foil flap is said to be lifted by an inhalation airflow, thereby exposing the medicament which is then said to be drawn along by the air flow. This embodiment is shown in FIG. 10. There is no disclosure of the foil being glued or welded over the cavity or of the foil creating an air-tight or moisture-tight seal.